There is evidence that glycoproteohormones such as thyrotropin (TSH) and the antiviral agent interferon exert their biological action, on sensitive cells, by interacting with membrane receptors which share common structural features. We plan to investigate the membrane composition in cells transformed with RNA tumor viruses (such as the Moloney murine leukemia-sarcoma virus and the Friend mouse erytroleukemia virus) which possess receptor sites for, and respond biologically to TSH and interferon. Attempts will be made to identify the mechanism whereby both effectors exert their action and establish the relationships between membrane binding and biological effects. Also we plan to compare the effect of viral transformation on TSH and cholera toxin binding and membrane composition of glycolipids and glycoproteins. Alterations of membrane composition will be correlated with abnormal response to TSH and cholera toxin stimulation of ions and amino acids transport, cyclic nucleotides accumulation and virus production.